The field of the present invention is pollution control systems for engine exhaust and particularly air introduction systems therefor.
With the advent of emissions control requirements for automobiles and motorcycles, a variety of systems have been developed to reduce the unburned hydrocarbons and carbon monoxide exhausted from an engine. One approach has been to introduce air into the exhaust passages at points adjacent the exhaust ports. In the area of the exhaust port, the temperature of the exhaust remains high enough so that the additional air will further oxidize the hydrocarbons and carbon monoxide, forming carbon dioxide and water.
As emission control requirements have been applied specifically to motorcycles, a need for a compact, uncomplicated and durable air introduction system has come to be recognized. The size and arrangement of motorcycle engines and associated equipment is such that a large system or a plurality of systems to provide air to V-type engines have been found to have substantial drawbacks. V-type engines used in motorcycles generally employ a transverse crankshaft and have the exhaust passages extending from the cylinders toward the front of the motorcycle from one bank and toward the rear of the motorcycle from the other bank. Heretofore, this normal exhaust arrangement has not lent itself to a compact, single air injection system. Alternatively, multiple air injection systems create needless weight, complication and resulting loss of reliability.
The need for compact air introduction equipment has also raised problems at the intersection of the air introduction passage and the exhaust passage. It is often inconvenient to provide a perpendicular intersection between these passages. As a result, the opening and associated passage may create weaknesses in the engine block or cylinder head. Additionally, the nozzle size of the hole in more tangential intersections of the passages is difficult to control in manufacture or free from carbon deposits during service. Thus, a plurality of practical difficulties have arisen in the provision of a efficient, compact and reliable air introduction arrangement for motorcycle exhaust systems.